Our commish got the owner that dropped Nomar to enable her to
reverse the drop, but was unable to do so- the ex Nomar owner
does not have an available roster spot, could that explain why
she could not reverse the drop ?

If he doesn't have an open roster spot, the owner that dropped Nomar has to choose a player for the commissioner to drop for him or drop a player himself so the commish can put Nomar on his roster. The commish can't override the maximum roster size.